Anti-lock brake systems for single-track motor vehicles are known and being used in practice (Journal VDI-Nachrichten, Apr. 29, 1988, page 25).
As compared to ABS systems used in four wheel vehicles, however, anti-lock braking of single-track motor vehicles causes considerable problems. When motorcycles are driven through curves, the superimposed longitudinal and transverse accelerations cause the greatest difficulties on braking. A wheel which transmits maximum lateral guiding forces between the roadway and the vehicle cannot at the same time transmit longitudinal forces, in other words brake performance. As a consequence, when driving through a curve the wheel will be retarded by too much brake pressure and therefore start to skid so that a fall practically is inevitable.
It is suggested in German Patent application No. P 38 38 520.7 published Nov. 14, 1988 that the transverse acceleration should be measured as the decisive parameter for adjustment of the threshold value for ABS control.
However, there are driving situations in which, although there is no transverse acceleration, braking still causes great problems. Such a situation exists, for example, when driving straight forward on a downward slope. In such a situation, as in travelling through a curve, the point of contact of the tire of the motorcycle leaves the center line (vertical plane of symmetry) of the motorcycle. If the driver applies the brakes in such a situation, either in a curve or on an inclined road surface on forward driving, the brake moment will cause a torque at the handle bar or guide of the vehicle because of the asymmetric position of the point of contact of the tire. This torque is directed such that it will attempt to erect the motorcycle out of its inclined position into the vertical position.
As the driver can hardly get control over this steering moment, the resulting situation is highly dangerous.